It has been previously reported (Kabara, The Pharmacological Effects of Lipids, ed. 1987, and Nutritional Biochemistry, Vol. 6, July, 1995) that certain lipids have antimicrobial effects. Those lipids reported to have antiviral and antibacterial activity are highly lipophilic, have HLB values of 2 to 4 and likely act by affecting the infectious organism's lipid envelope or membrane leading to changes in the organism's permeability resulting in loss of infectivity.
The high lipophilicity of those lipids, however, makes it difficult to carry out prophylactic studies because the lipids are insoluble in aqueous solutions. The solubility problems can be overcome to some extent through the use of non-aqueous solvents such as ethanol or dimethylsulfoxide (DMSO) (Isaacs, Litov, and Thormar, Nutritional Biochemistry, 1995). Such solvents, in many instances, are inappropriate for use in humans or animals. By way of example, ethanol and DMSO are contraindicated for use in infants.
Still another problem associated with the use of existing antimicrobial lipids is that the antimicrobial action is inhibited or greatly reduced in the presence of proteins (Kabara, The Pharmacological Effects of Lipids, ed. 1987; and U.S. Pat. No. 4,002,775, Fatty Acids and Derivatives as Antimicrobial Agents, 1977). Thus, such lipids cannot be administered together with proteins such as are present in enteral nutritional formulations. There continues to be a need in the art therefore for antibacterial lipids that are soluble in aqueous formulations and those whose antibacterial activity is not adversely affected by the presence of intact protein.